One question per member to ensure Dr. Sowers isn't overloaded with questions. Ensure your question is well presented, readable and worthwhile and please read the coverage of the reveal here: http://forum.nasaspaceflight.com/index.php?topic=37251.0 - to ensure you don't ask a question already addressed (or that you ensure it asked for clarification of an answer).

Thanks very much for doing this with us. Can you talk about any timelines or capabilities for Vulcan human launch? That wasn't touched on at all during the press conference, but with CST-100/Atlas making a lot of news, I'm sure things like pad access etc are in the works.

Thank you very much for taking the time to answer these questions. Tory Bruno has stated that the SMART Reuse system won't be used on the Vulcan initially, but will be phased in. How long do you think it will take for them to start using it? And do you believe it will be done gradually, alla SpaceX or will it be much more rapid, say one or two experimental launches, then going full engine reuse?

Dr. Sowers, thank you again for coming back to answer more questions about your new rocket. I can't wait to watch it come together over the next few years, and hope Blue Origin can be persuaded to release engine testing videos.

If I recall correctly, ACES was a modular family that would fly with varying numbers of engines and even varying sizes of tanks to accomodate different mission requirements. Is that still the plan for the future Vulcan upper stage?

I watched the presentation and one thing struck me about upper stage being proposed. Didn't the original ACES paper have them switching from the current Centaur Stainless tank to a larger Al-Li tank. Tory made it quite clear the new upper stage being proposed will use new Stainless tanking.

Care to elaborate on the ACES's switch from the new tank using Al-Li to Stainless? Why is it superior? Better mass fraction? Easier to make? Cheaper to make? 70 years of experience manufacturing balloon tanks with Stainless?

Thanks Dr.Sowers for taking the time to answer our questions. We're all very excited about the preliminary details revealed in today's announcement.

My question is: What key factors set the architecture in favor of multiple solid boosters instead of a multiple common core configuration as seen on other heavy lifters such as the Delta IV Heavy, Falcon Heavy, Angara V?

My question is, how will the vehicle be delivered and processed at the pad? First transportation; will the stages be transported by barge or by air from the factory? For launch site integration; will it be like Atlas V (vertical rocket integration and a mobile transporter to the pad), Delta IV (horizontal rocket integration, erected at the pad and vertical payload integration with a mobile service tower) or like Falcon 9 (horizontal integration and erected at the pad)?

why will Vulcan start out with an upper stage based on RL-10 instead of a BE-3?

There is certainly more experience with the BE-3 engine already, than with the BE-4 engine you plan to use in the 1st stage. BE-3 has already gone through acceptance testing while BE-4 has yet to be build, not to say test-fired. You could start developing an upper stage with a BE-3 engine right away and demonstrate it on either an Atlas or Delta rocket.

Same question in other words: If you are preprared to use an engine in development like the BE-4 in 2019, why is it important to first gather flight experience with the BE-3 before using it with the new rocket some time in 2023?

I'm excited to see the progress on this new rocket, and glad you guys are able to talk more openly about orbital refueling and such! Hopefully I get a chance to say hi when we're down at the symposium tomorrow.

My question is sort of boring, but do you have any numbers you can publish about expected performance for Vulcan, both with various numbers of strapons and the existing Centaur stage, and then with various numbers of strapons and the new ACES stage?